As a material including water as a medium and having high biocompatibility, a hydrogel is used in a wide range of fields, and various kinds of hydrogels including a hydrogel formed of a high molecular weight compound and a hydrogel formed by the self-assembly of a low molecular weight compound have been studied.
Among these, recently, regarding a low molecular weight hydrogelator formed of a low molecular weight compound, the functionality thereof has attracted much attention and the study thereof has been vigorously carried out although it is difficult to elucidate a mechanism for the self-organization of a low molecular weight compound in water; and to make a molecular design. As a result, some low molecular weight hydrogelators have been developed (Non-Patent Documents 1 and 2). Most of the low molecular weight hydrogelators are amphipathic compounds including a long-chain alkyl group, which is a hydrophobic moiety, and a hydrophilic moiety. Examples of the hydrophilic moiety include an amino acid (Non-Patent Document 3), a peptide (Patent Documents 1 and 2), a monosaccharide or a polysaccharide (Non-Patent Documents 4 and 5), and a polyol (Non-Patent Document 6). In addition, a low molecular weight gelator (Non-Patent Document 7) using the fact that a peptide formed of valine is likely to have a β-sheet structure has also been proposed.
In addition, a low molecular weight hydrogelator that can turn an aqueous alcohol solution or an aqueous organic solvent solution into a gel; or a low molecular weight hydrogelator that cannot turn water alone or an organic solvent alone into a gel but can turn an aqueous alcohol solution or an aqueous organic solvent solution into a gel, has been reported.
With such a low molecular weight hydrogelator, a hydrogel can be formed by heating and stirring the hydrogelator and water serving as a medium under a heating condition of about 100° C. to dissolve and disperse the gelator in water; and leaving this solution to stand at room temperature.